This invention relates to chewing gum products and to methods of using same. More particularly, this invention relates to chewing gum products and methods of using same, wherein the chewing gum products are capable of remineralizing subsurface dental lesions and/or mineralizing exposed dentinal tubules so as to counteract caries and/or hypersensitivity, respectively.
The primary component of the enamel and dentin in teeth is calcium phosphate in the form of calcium hydroxyapatite. This material is highly insoluble at normal oral pHs. However, carious lesions can form in teeth when the teeth are subjected to acids produced from the glycolysis of sugars by the action of various oral bacteria. This is because calcium phosphate salts are more soluble in acidic media.
Saliva is supersaturated with respect to calcium and phosphate ions. Saliva, therefore, helps protect teeth against demineralization and can slowly remineralize teeth which have become demineralized by acids. It is well known that the presence of fluoride ions can enhance the natural remineralization process and this is one of the accepted mechanisms by which fluoride toothpastes and rinses protect against caries. The efficacy of fluoride-containing toothpastes and rinses to remineralize teeth is limited by the modest levels of calcium and phosphate in saliva. It is evident from the prior art that it is highly desirable to increase the available concentration of calcium and phosphate ions in the oral cavity to speed up the remineralization process. However, because of calcium phosphate's low solubility at the pH of saliva, the addition of higher levels of dissolved calcium and phosphate ions is not easily accomplished.
Remineralization of dental enamel has been carried out experimentally, both in vivo and in vitro. Some studies have concentrated on the remineralizing properties of saliva and synthetic solutions supersaturated with respect to hydroxyapatite. Such studies comprise the subject matter of U.S. Pat. Nos. 3,679,360 (Rubin) and 4,097,935 (Jarcho).
Generally, the supersaturated solutions or slurries used in the Rubin and Jarcho patents for remineralization experiments have been prepared from a single form of calcium phosphate. When a carious lesion is flooded with one of these supersaturated solutions, the calcium and phosphate ions in the form of precipitated hydroxyapatite remineralize the lesion.
However, these solutions are impractical for use for several reasons. First, the amounts of calcium and phosphate ions available for remineralization in these supersaturated solutions are too low. It is reported that it takes approximately 10,000 unit volumes of the usual supersaturated solution to produce one unit volume of mineral. Thus, remineralization by this method requires both an excessive volume of fluid and an excessive number of applications. The supersaturated solutions are inherently limited in this respect because they cannot maintain their supersaturated state. When the hydroxyapatite precipitates out to the point where the solution is no longer supersaturated, new supersaturated solution must be introduced or the remineralization process stops.
Another problem with single calcium phosphate slurries is that as the hydroxyapatite precipitates out of solution, the pH of the solution changes. Unless the old solution is removed from contact with the tooth material, the solution may become too acidic or alkaline and damage the dental tissue.
U.S. Pat. Nos. 4,083,955 (Grabenstetter et al) and 4,397,837 (Raaf et al) disclose processes utilizing various dentifrices, including chewing gums, for remineralizing demineralized enamel by the consecutive treatment of tooth surfaces with separate solutions containing calcium ions and phosphate ions. Fluoride ions may be present in the phosphate solutions. It is immaterial which ionic solution is used to treat the teeth first. By sequentially applying calcium and phosphate ions to the tooth surface, high concentrations of the ions are able to diffuse or penetrate into lesions in solution form, where the ions precipitate as a calcium phosphate salt when ions from the second treatment solution diffuse in. While apparently successful, this method involves the inconvenience of employing two different chewing portions, one containing the calcium ions and the other the phosphate ions. This method could be confusing because of the necessity of ensuring the proper sequence of gum portions and also inconvenient due to the plurality of sequential applications which can be found to be time consuming.
U.S. Pat. Nos. 5,037,639 and 5,268,167 (both to Tung) disclose the use of amorphous calcium compounds such as: amorphous calcium phosphate (ACP), amorphous calcium phosphate fluoride (ACPF) and amorphous calcium carbonate phosphate (ACCP) for use in remineralizing teeth. These amorphous compounds or solutions which form the amorphous compounds when applied either onto or into dental tissue prevent and/or repair dental weaknesses such as dental caries, exposed roots and dentin sensitivity. The compounds are claimed to have high solubilities, fast formation rates and fast conversion rates (to apatite).
According to the Tung patents, remineralization is accomplished by bringing the amorphous compound into contact with the dental tissue. This can be done directly, i.e., putting an amorphous compound directly on the tooth, or indirectly through a carrier, i.e., incorporating the amorphous compound in a carrier such as a gel, a chewing gum, or a toothpaste and applying the carrier to the dental tissue. Once contact is established with the tooth, the amorphous calcium phosphate compounds will recrystallize to the less soluble apatite form in the lesion and reform the tooth. However, under conditions where amorphous calcium phosphate compounds are stable, the quantity of calcium and phosphate released is relatively low and, therefore, remineralization is slower than desirable.
International Patent WO 94/18938 (Greenberg) teaches the addition of calcium glycerophosphate to a chewing gum. The calcium glycerophosphate is said to increase calcium and phosphate concentrations in plaque, increasing remineralization and decreasing demineralization. It may also inhibit large drops in pH in plaque and interfere with metabolism of S. mutans. A problem with this technology is that the glycerophosphate ion has to hydrolyze and release free phosphate ions before it can participate in the remineralization process. Hydrolysis occurs in the mouth due to the presence of phosphatase enzymes. However, the process is slow. The high concentration of calcium ions supplied by the calcium glycerophosphate therefore has time to dissipate before sufficient phosphate can be released to produce maximum remineralization.
Thus, a problem with known remineralization compositions and techniques is that there is not a one-part, stable remineralizing composition that may be suitably prepared as a chewing gum and the like which is not negatively affected by a rise in pH or temperatures and which can efficiently remineralize teeth.
There is a need for a method of remineralizing dental enamel which uses a stable, single-part remineralizing chewing gum composition which does not require excessive amounts of calcium and phosphate salts or inordinately long, frequent or sequential exposure times.
Accordingly, a primary object of this invention is to provide a single-part, stable chewing gum product which is capable of remineralizing subsurface lesions in teeth and/or mineralizing exposed dentinal tubules in teeth.
A further object of this invention is to provide a chewing gum product having the aforementioned capabilities, wherein the chewing gum product is also easily usable by the consumer and, in terms of flavor and appearance, does not differ significantly from customary chewing gums.
These and other objects which are achieved according to the present invention can be discerned from the following description.